/*
 * Copyright 2016 The Cartographer Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "cartographer/io/proto_stream.h"

#include "glog/logging.h"

namespace cartographer
{
    namespace io
    {

        namespace
        {

            // First eight bytes to identify our proto stream format.
            const uint64 kMagic = 0x7b1d1f7b5bf501db;

            void WriteSizeAsLittleEndian(uint64 size, std::ostream *out)
            {
                for (int i = 0; i != 8; ++i)
                {
                    out->put(size & 0xff);
                    size >>= 8;
                }
            }

            bool ReadSizeAsLittleEndian(std::istream *in, uint64 *size)
            {
                *size = 0;
                for (int i = 0; i != 8; ++i)
                {
                    *size >>= 8;
                    *size += static_cast<uint64>(in->get()) << 56;
                }
                return !in->fail();
            }

        } // namespace

        ProtoStreamWriter::ProtoStreamWriter(const std::string &filename) : out_(filename, std::ios::out | std::ios::binary)
        {
            WriteSizeAsLittleEndian(kMagic, &out_);
        }

        void ProtoStreamWriter::Write(const std::string &uncompressed_data)
        {
            std::string compressed_data;
            common::FastGzipString(uncompressed_data, &compressed_data);
            WriteSizeAsLittleEndian(compressed_data.size(), &out_);
            out_.write(compressed_data.data(), compressed_data.size());
        }

        void ProtoStreamWriter::WriteProto(const google::protobuf::Message &proto)
        {
            std::string uncompressed_data;
            proto.SerializeToString(&uncompressed_data);
            Write(uncompressed_data);
        }

        bool ProtoStreamWriter::Close()
        {
            out_.close();
            return !out_.fail();
        }

        ProtoStreamReader::ProtoStreamReader(const std::string &filename) : in_(filename, std::ios::in | std::ios::binary)
        {
            uint64 magic;
            if (!ReadSizeAsLittleEndian(&in_, &magic) || magic != kMagic)
            {
                in_.setstate(std::ios::failbit);
            }
            CHECK(in_.good()) << "Failed to open proto stream '" << filename << "'.";
        }

        bool ProtoStreamReader::Read(std::string *decompressed_data)
        {
            uint64 compressed_size;
            if (!ReadSizeAsLittleEndian(&in_, &compressed_size))
            {
                return false;
            }
            std::string compressed_data(compressed_size, '\0');
            if (!in_.read(&compressed_data.front(), compressed_size))
            {
                return false;
            }
            common::FastGunzipString(compressed_data, decompressed_data);
            return true;
        }

        bool ProtoStreamReader::ReadProto(google::protobuf::Message *proto)
        {
            std::string decompressed_data;
            return Read(&decompressed_data) && proto->ParseFromString(decompressed_data);
        }

        bool ProtoStreamReader::eof() const
        {
            return in_.eof();
        }

    } // namespace io
} // namespace cartographer
